Color filter composition

ABSTRACT

A color filter composition, a color display device, and a production method of the same with which an increase of the luminance, an increase of the contrast, an increase in the range of color reproduction, and an improvement of the function for preventing reflection of outside light can be achieved. The color filter composition has a spectral characteristic allowing specific light of the visible region to pass therethrough and is composed of fine particles of an inorganic metal oxide containing 15 percent by weight or less of particles having a particle size of 0.1 μm or more based on the weight of all of the particles and contains 70 percent by weight or more of particles having a particle size of 0.01 μm to 0.07 μm based on the weight of all of the particles. A color filter is formed on an inner surface of a panel of a display device by screen printing or heat transfer printing by using this color filter composition.

CROSS-REFERENCE TO RELATED APPLICATION

This Application is a Divisional of prior application Ser. No.08/825,801, filed Apr. 2, 1997, now U.S. Pat. No. 5,952,137.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a color filter composition, a colordisplay device, and a production method of same.

2. Description of the Related Art

In recent years, there has been much studies on differentiation ofproducts through improvements in the performance of the color displaydevice, represented by a vacuum fluorescent light emitting device (VFD),an electrofluorescent light emitting device (EL), a photodiode lightemitting device (LED), and other image tubes or a plasma display device(PDP), a field emission display device (FED), a cathode ray tube (CRT),and other picture tubes and on a reduction of costs by reexamination ofthe mass production system.

In a CRT such represented by a Braun tube of a television set, anelectron beam emitted from an electron gun strikes the surface of thelayer of fluophors to energize the fluophor particles and cause emissionof light for the display. The diversification of various kinds of visualapparatuses using CRTs accompanying the advances in the field ofelectronics in recent years has led to various improvements anddevelopments.

For example, the fluophors used in the CRTs are improved in color purityby coating an inorganic pigment on the fluophor particles. However,since the coated pigment is adhered to the fluophor particles in stateand not formed as a separate layer, the luminance of the emission of thefluophors has been lowered.

In order to compensate for this state, it may be considered to raise theoutput of the electron beam irradiated to the fluophor surface, but thismethod is liable to lead to a deviation in color due to the thermalexpansion of the shadow mask and a reduction of the service life of thefluophors.

Further, a color display device provided with a color filter containingat least one type of metal compound of nickel and cobalt and also usinga dye has been proposed (Japanese Unexamined Patent Publication (Kokai)No. 2-46403).

A dye filter, however, is insufficient in the heat resistance and lightresistance, so a sintering step cannot be used and thus it is used in alaminated glass system. Further, a color display device of this dyefilter system cannot be used for the purpose of an outdoor videoapparatus.

Also, in the process for production of a color CRT having a fluophorsurface on the inner surface of a face plate, there is known a processfor production of a CRT equipped with a color filter wherein a ultrafineparticle pigment dispersion is coated on the inner surface of a faceplate made of glass to form a pigment layer and then a fluophersuspension is further coated to form a laminate layer, then collectiveexposure via the shadow mask and development for patterning(photolithography) are carried out.

Nevertheless, this photolithography method has disadvantages of thethroughput and stability. Namely, a UV crosslinking type vehicle(PVA/ADC-base) has a pot life, so it is impossible to avoid a coarseningof the pigment due to an aging by a dark reaction. This leads to areduction of the workability due to the frequency of exchange of thedispersions and a poor stability of the quality (deterioration oftransmittance).

Further, a difficult point at the time of coating of the laminate layersof the color filter and the fluophor layer has been the fact that anupper coating layer (10 μm≦fluophor thick film) invades a lower coatinglayer (3 μm≧color filter thin film) due to a double coating by the samevehicle-base. Accordingly, it is hard to obtain a good layer-separatedcoating film, which has led to a fluctuation in the quality.

Further, in such a color display device equipped with the color filter,for improvement of the contrast, it is necessary to raise the coloringdensity of the color filter. Since coarse particles of 1 μm or more aremixed in and also the distribution of the particle size is wide at theconventional pigment dispersion level, the transmittance of light isdegraded. Thus there has been a limit to raising the contrast andincreasing the color reproduction range.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a color filtercomposition, a color display device, and a production method of the samewith which an increase of the luminance, an increase of the contrast, anincrease of the color reproduction range, and an improvement of theability to prevent reflection of outside light can be achieved in acolor display device.

To attain the above object, the color filter composition according tothe present invention has a spectral characteristic allowing specificlight of the visible region to pass therethrough and comprises fineparticles of an inorganic metal oxide containing 15 percent by weight orless of particles having a particle size of 0.1 μm or more based on theweight of all of the particles and containing 70 percent by weight ormore of particles having a particle size of 0.01 μm to 0.07 μm based onthe weight of all of the particles.

Preferably, the light transmittance of the light absorbing region of thecolor filter composition after sintering is 20 percent or less, and thelight transmittance of the light transmission region is 50 percent ormore.

Preferably, the inorganic metal oxide contains at least one of ironoxide, titanium oxide, nickel oxide, cobalt oxide, zinc oxide, aluminumoxide, and chromium oxide. For example, as the red color filtercomposition, preferably Fe₂ O₃ is contained. As the green color filtercomposition, TiO₂ --NiO--CoO--ZnO or CoO--CrO--TiO₂ --Al₂ O₃ ispreferably contained. As the blue color filter composition, preferablyCoO--Al₂ O₃ is contained.

The color display device according to a first aspect of the presentinvention is a color display device comprising a transparent panel; ared fluophor layer, a green fluophor layer, and a blue fluophor layerprovided on an inner surface of the transparent panel and respectivelyemitting lights of red, green, and blue by irradiation of an energybeam; and a color filter which is provided between one of the fluophorlayers and the transparent panel and has a high transmission property ina wavelength region of specific light of the visible region, wherein thecolor filter includes fine particles of an inorganic metal oxidecontaining 15 percent by weight or less of particles having a particlesize of 0.1 μm or more based on the weight of all of the particles andcontaining 70 percent by weight or more of particles having a particlesize of 0.01 μm to 0.07 μm based on the weight of all of the particles.

A color display device according to a second aspect of the presentinvention is a color display device comprising a transparent panel;three types of color filters which are provided on the inner surface ofthe transparent panel with a predetermined pattern and respectivelyselectively allow lights of red, green, and blue to pass therethrough;and single color fluophor layers which are provided on the inner surfaceof the three types of color filters and emit a single type of light bythe irradiation of an energy beam, wherein the color filters includefine particles of an inorganic metal oxide containing 15 percent byweight or less of particles having a particle size of 0.1 μm or morebased on the weight of all of the particles and containing 70 percent byweight or more of particles having a particle size of 0.01 μm to 0.07 μmbased on the weight of all of the particles.

The production method of the color display device according to the firstaspect of the present invention is characterized in that screen printingis carried out by using the color filter composition to form the colorfilter layer and the fluophor layer on the inner surface of the panel.Further, this production method is characterized in that no-coloredfluophor is used which emits single color fluorescence. Namely, thisproduction method is characterized in that it comprises the steps ofscreen printing three types of color filters which respectivelyselectively allow the lights of red, green, and blue to passtherethrough on the inner surface of the transparent panel with apredetermined pattern and forming a single color fluophor layer emittinga single type of light by irradiation of the energy beam on the innersurface of the three types of color filters by the screen printing, fineparticles of an inorganic metal oxide containing 15 percent by weight orless of particles having a particle size of 0.1 μm or more based on theweight of all of the particles and containing 70 percent by weight ormore of particles having a particle size of 0.01 μm to 0.07 μm based onthe weight of all of the particles being contained in a pigment pastefor screen printing the color filters.

The production method of the color display device according to thesecond aspect of the present invention is characterized in that heattransfer printing is carried out by using the color filter compositionto simultaneously form the color filter layer and the fluophor layerformed on the inner surface of the panel. Namely, this production methodcomprises the steps of forming a peeling layer on the surface of a heattransfer use substrate sheet; forming a red fluophor layer, a greenfluophor layer, and a blue fluophor layer respectively emitting thelights of red, green, and blue by irradiation of an energy beam on thesurface of the peeling layer; forming three types of color filters whichrespectively selectively allow the lights of red, green, and blue topass therethrough on the surfaces of the fluophor layers of therespective colors corresponding to the fluophor layers of the respectivecolors; forming a thermal sealing agent layer on the surface of thecolor filters to form a transfer sheet; and bringing the thermal sealingagent layer of the transfer sheet into close-contact with thetransparent panel, performing the heat transfer printing, and formingthe fluophor layer equipped with the color filters on the inner surfaceof the transparent panel, fine particles of an inorganic metal oxidecontaining 15 percent by weight or less of particles having a particlesize of 0.1 μm or more based on the weight of all of the particles andcontaining 70 percent by weight or more of particles having a particlesize of 0.01 μm to 0.07 μm based on the weight of all of the particlesbeing contained in a pigment paste for forming the color filters.

If a color filter of a color display device is formed by using the colorfilter composition according to the present invention, since the filtercomposition is comprised by the inorganic metal oxide, it is excellentin heat resistance and the filter layer is not deteriorated even at thetime of the production of a CRT or other color display deviceaccompanied with a heat treatment step of about 500° C. Further, in thepresent invention, since the color filter is comprised by fine particlesof an inorganic metal oxide, the transmittance of the obtained colorfilter is improved and also the luminance is improved. For this reason,it becomes possible to raise the coloring density of the color filter,which contributes to the increase of the contrast and an increase of thecolor reproduction range.

In the present invention, by forming the color filter and the fluophorlayer by the screen printing or the heat transfer printing, a laminatestructure in which the color filter and the fluophor layer are wellseparated is obtained, the luminance of the emission of the fluophors isnot lowered, and the image quality is improved and, at the same time,there is a contribution to the stability of the quality of the colordisplay device.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects and features of the present invention willbecome clearer from the following description of the preferredembodiments made with reference to the attached drawings, in which

FIG. 1 is a schematic view of a color CRT according to an embodiment ofthe present invention;

FIG. 2 is a sectional view of principal parts of an inner surface of apanel shown in FIG. 1;

FIGS. 3A to 3C are views showing spectral transmittance characteristicsof a red, green and blue color filters respectively according to anembodiment of the present invention;

FIG. 4 is a sectional view of the principal parts of a color flat screendisplay device according to another embodiment;

FIGS. 5A to 5C are graphs showing particle size distributions of thecolor filter composition according to an embodiment of the presentinvention;

FIGS. 6A to 6C are graphs showing the transmittance characteristics ofthe color filter according to an embodiment of the present invention;

FIG. 7 is a graph showing the transmittance characteristic of aconventional color filter; and

FIG. 8A is a graph showing a range of color of a CRT which can bereproduced using a color filter according to an embodiment of thepresent invention; and FIG. 8B is a graph showing the range of the colorof a CRT which can be reproduced using a color filter according to aconventional example.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Below, a color filter composition, color display device, and productionmethod according to the present invention will be explained in detailbased on the embodiments shown in the drawings.

First Embodiment

The embodiment shown in FIG. 1 is obtained by applying the presentinvention to a color CRT as a color display device.

As shown in FIG. 1, a color CRT 10 of the present embodiment has a panelglass 12 in which a fluophor surface is formed on the inner surface andfunnel glass 14 which is bonded to this panel glass and in which anelectron gun 16 is accommodated in a neck portion. An electron beamemitted from the electron gun 16 is biased by a biasing yoke and strikesthe fluophor surface through an aperture grill 20 serving as the shadowmask mounted on the inner surface side of the panel glass 12 to causeemission.

The panel glass 12 is comprised by a glass having a high lighttransmittance (for example 90 percent or more transmittance) having afluophor surface formed on the inner surface thereof. As the panel glasshaving a high light transmittance, use is made of a panel glass obtainedby adhering a safety panel of a high transmittance to the surface of aglass panel of a high transmittance. As the panel glass of the hightransmittance, more specifically, use can be made of a combination of aclear safety panel (EIAJ code JS520AA01) with a tint panel (EIAJ codeJP520AG11) made by Nihon Denki Itagarasu Corp.

As shown in FIG. 2, in the present embodiment, black stripes (carbonstripes) 2 are formed on the inner surface of the panel glass 12 atpredetermined intervals. A red (R) fluophor layer 15R, a green (G)fluophor layer 15G, and a blue (B) fluophor layer 15B are alternatelyarranged between these stripes 2 in this order. These fluophor layers15R, 15G, and 15B are covered by for example an aluminum film(illustration omitted).

In the present embodiment, between the fluophor layers 15R, 15G, and 15Band the panel glass 12, a red color filter 4R, a green color filter 4G,and a blue color filter 4B having a high transmittance in a wavelengthregion of lights of the respectively corresponding colors are mounted.

The red color filter 4R is comprised by a color filter composition whichcontains as a main component Fe₂ O₃ as the inorganic metal oxide andcontains 15 percent by weight or less of particles having a particlesize of 0.1 μm or more based on the weight of all of the particles andcontains 70 percent by weight or more of particles having a particlesize of 0.01 μm to 0.07 μm based on the weight of all of the particles.The green color filter 4G is comprised by a color filter compositionwhich contains as a main component TiO₂ --NiO--CoO--ZnO (1:1:1:1) andcontains 15 percent by weight or less of particles having a particlesize of 0.1 μm or more based on the weight of all of the particles andcontains 70 percent by weight or more of particles having a particlesize of 0.01 μm to 0.07 μm based on the weight of all of the particles.The blue color filter 4B is comprised by a color filter compositionwhich contains as a main component CoO--Al₂ O₃ (1:1) and contains 15percent by weight or less of particles having a particle size of 0.1 μmor more based on the weight of all of the particles and contains 70percent by weight or more of particles having a particle size of 0.01 μmto 0.07 μm based on the weight of all of the particles.

The thickness of the color filter d is not particularly limited, but ispreferably 0.1 μm≦d≦3.0 μm, more preferably about 0.5 μm≦d≦2.0 μm. Ifthe film thickness d is less than 0.1 μm, the effect of improvement ofthe contrast due to the provision of the filter cannot be expected andit becomes difficult to obtain a filter having a uniform film thicknessas a whole, while if the film thickness d exceeds 3.0 μm, the reductionof the luminance becomes large. Neither of these is desirable.

FIG. 3A shows a curve of the spectral transmittance of the red colorfilter 4R, FIG. 3B shows a curve of the spectral transmittance of thegreen color filter 4G, and FIG. 3C shows a curve of the spectraltransmittance of the blue color filter. In these filters, as shown inFIGS. 3A to 3C, the light transmittance of the light absorbing region is20 percent or less, and the light transmittance of the lighttransmission region is 50 percent or more.

In the present embodiment, it is desired in obtaining a betterchromaticity and luminance that a layer represented by the followinggeneral formula be used as the red (R) fluophor layer 15R forcombination in the above filter:

A:B

where, A is Y₂ O₂ S, Y₂ O₃, or a mixture of the same and

B is Eu or a mixture of Eu and Sm,

where the Eu concentration [Eu] in the fluophor layer is represented as0.1 mol %≦[Eu]≦6.0 mol %.

More specifically, there are a fluophor layer containing ayttrium-oxi-sulfide as a main crystal and containing europium as anadditive, a fluophor layer containing the yttrium-oxi-sulfide as themain crystal and containing europium and samarium as the additives, andso on.

Most desirably, as the red fluophor layer 15R, use is made of a fluophorlayer represented by the above general formula in which the Euconcentration [Eu] is 2.8 mol %≦[Eu]≦4.7 mol % and the film thickness dof the red color filter is determined as 0.5 μm≦d≦2.0 μm.

As the green fluophor layer 15G, use is made of a fluophor layercontaining for example zinc sulfide as the main crystal and containingcopper, aluminum, etc. as additives. As the blue fluophor layer 15B, forexample, use is made of a fluophor layer containing zinc sulfide as themain crystal and silver or the like as the additive.

Next, in the present embodiment, one example of a method of providingthe fluophor surface on the inner surface of the panel glass is shown.

First, the black stripes 2 shown in FIG. 2 comprised by carbon black orthe like as a substance not emitting light but absorbing light areformed. In the formation of the black stripes 2, the panel glass iswashed and a photo resist comprised of a photosensitive agent and awater-soluble polymer such as a polyvinyl alcohol (PVA) is coated on theinner surface of the panel glass 12. This is dried to form a resistcoating film. Next, the predetermined part of the resist coating film iscured by exposure using the mask.

Next, the unexposed part of the resist coating film is removed bydevelopment. The result is dried to form stripes of resist coating film.Then a carbon black suspension is coated on the entire surface of thepanel glass. This is then dried and then a reversal solution is coatedand the surface is developed and dried, thereby to form black stripes 2made of carbon black. Note that it is also possible to simultaneouslyform the black stripes 2 together with the color filter and the fluophorlayer by the heat transfer printing mentioned later.

To form the color filter and the fluophor layer on the inner surface ofthe panel glass by the heat transfer printing, first a transfer sheet isformed. So as to form the transfer sheet, a peeling layer is formed onthe surface of a substrate sheet for heat transfer. On the surface ofthis peeling layer, the red fluophor layer 15R, the green fluophor layer15G, and the blue fluophor layer 15B emitting the lights of red, green,and blue mentioned before are formed with a predetermined pattern. Next,the three types of color filters 4R, 4G, and 4B which respectivelyselectively allow the lights of red, green, and blue to passtherethrough are respectively formed on the surfaces of the fluophorlayers 15R, 15G, and 15B of the respective colors with the patternscorresponding to the fluophor layers of the respective colors. Next, athermal sealing agent layer is formed on the surfaces of the colorfilters 4R, 4G, and 4B to complete the transfer sheet.

The thermal sealing agent layer of this transfer sheet is brought intoclose contact with the transparent panel glass 12 and heat transferprinting is performed to form and a fluophor layer equipped with thecolor filters on the inner surface of the panel glass 12 as shown inFIG. 2.

After the fluophor layers of the three colors of red, green, and blueare formed in this way, an intermediate film is formed on them. Theintermediate film is comprised by an organic film, flattens the fluophorsurface, and facilitates the coating of the aluminum thin film layer asthe metal thin film layer in the later steps. After the prebaking andthe baking treatment at the frit sealing in the later step, theintermediate film is removed together with the PVA etc. through thealuminum film.

Thereafter, an aluminum thin film layer serving as the metal thin filmlayer is coated on the intermediate film. By forming the aluminum thinfilm layer, the luminance of the display screen is improved andionization can be prevented.

Thereafter, the prebaking is carried out, the aperture grill is mountedon the inner surface of the panel glass, and then the seal edge face ofthe panel glass and the seal edge face of the funnel glass are fritseal-bonded. It is also possible to perform the prebaking after mountingthe aperture grill. By this prebaking and the baking treatment (heattreatment) at the frit sealing, the components of the intermediate filmand the organic component contained in the fluophor stripes (fluophorlayer) are removed from the fluophor surface through the aluminum filmand the coating film of the fluophor surface is fixed.

In the present embodiment, since the filter composition is comprised byan inorganic metal oxide, it is excellent in the heat resistance. Thefilter layer is not deteriorated even at the time of production of a CRTor other color display device etc. accompanied with a heat treatmentstep of about 500° C. Further, in the present embodiment, since thecolor filter is comprised by fine particles of an inorganic metal oxide,the transmittance of the obtained color filter is improved and also theluminance is improved. For this reason, it becomes possible to raise thecoloring density of the color filter which contributes to the increaseof the contrast and increase of the color reproduction range.

Further, by forming the color filter and the fluophor layer by the heattransfer printing, a laminate structure in which the color filters 4R,4G, and 4B and the fluophor layers 15R, 15G, and 15B are well separatedas layer is obtained, and the luminance of the emission of the fluophorsis not lowered, the image quality is improved and, at the same time,there is a contribution to the stability of the quality of the CRT.

Second Embodiment

Next, an explanation will be made of an embodiment applying the presentinvention to a color flat screen display device utilizing field emissiontype microcathodes as the color display device.

As shown in FIG. 4, a color flat screen display device 60 of the presentembodiment is a display device which performs the image display byirradiating electron beams emitted from a plurality of field emissiontype microcathodes 50 arranged on a semiconductor substrate 30 in theform of a matrix by scanning to a fluophor surface formed on the innersurface of a transparent panel 22 such as a glass substrate to causeemission of light. The space between the semiconductor substrate 30 andthe transparent substrate 22 is held at a high vacuum. On the fluophorsurface formed on the inner surface of the transparent panel 22, blackstripes 2 and color filters 4R, 4G, and 4B similar to those of theembodiment shown in FIG. 2 are formed, but the fluophor layer 15 isconstituted by a single color fluophor layer 15 emitting not three typesof colors, i.e., R, G, and B. but a single type of light. Further, theformation of the color filters 4R, 4G, and 4B and the single colorfluophor layer 15 is different from the first embodiment in the pointthat the screen printing is used. The single color fluophor layer 15 isnot particularly limited, but ZnO:Zn emitting for example a blue greencolor may be used.

Next, one example of the method for producing the microcathodes 50 onthe semiconductor substrate 30 will be explained.

In the present embodiment, first, an insulation layer 31 and gateelectrodes 35 are sequentially formed on the semiconductor substrate 30.As the semiconductor substrate 30, for example, a single crystal siliconsubstrate is used.

In the present embodiment, the insulation layer 31 is constituted by amain insulation layer 32 and a hydrogen-containing layer 33. The maininsulation layer 32 is comprised by silicon oxide formed by for examplea CVD process, while the hydrogen-containing layer 33 is comprised by ahydrogen-containing silicon oxide formed by plasma CVD performedsubsequent to the CVD for forming the main insulation layer 32. The maininsulation layer 32 comprised by the silicon oxide film is formed by CVDunder for example the following conditions. The conditions are asfollows: as the CVD material gas, SiH₄ and O₂ are used, the flow ratioof SiH₄ /O₂ is for example 300/300 SCCM, the atmospheric pressure is forexample 300 Pa, the substrate temperature is for example 400° C., andthe film forming time is for example 4 minutes. The film thickness ofthe main insulation layer 32 is for example 0.8 μm.

Subsequently, the hydrogen-containing layer 33 comprised by ahydrogen-containing silicon oxide film to be formed by the plasma CVD isformed by plasma CVD of for example the following conditions. As theplasma CVD material gas, SiH₄ and O₂ are used, the flow ratio of SiH₄/O₂ is for example 400/300 SCCM, the atmospheric pressure is for example300 Pa, the substrate temperature is for example 350° C., and the filmforming time is for example one minute. The film thickness of thishydrogen-containing layer 33 is for example 0.2 μm.

The gate electrodes 35 are not particularly limited, but in the presentembodiment, use is made of a "polycide" film, that is, a laminate filmof an n conductive polycrystalline silicon film 34 and a tungstensilicide (WSix) film 36. The gate electrodes 35 act as the grid of forexample the microcathodes. Note that, the step of forming an emitterelectrode to be formed on the surface of the semiconductor substrate 30has been omitted.

The thickness of the polycrystalline silicon film 34 is for example 100to 300 nm. The thickness of the tungsten silicide film 36 is for example150 to 300 nm. The polycrystalline silicon film 34 and the tungstensilicide film 36 are formed by for example CVD. The polycrystallinesilicon film 34 is formed under for example the following conditions. Asthe plasma CVD material gas, SiH₄ and PH₃ are used, the flow ratio ofSiH₄ /PH₃ is for example 500/0.3 SCCM, the atmospheric pressure is forexample 100 Pa, and the substrate temperature is for example 500° C. Thetungsten silicide film 36 is formed under for example the followingconditions. As the plasma CVD material gas, WF₆, SiH₄, and He are used,the flow ratio of WF₆ /SiH₄ /He is for example 3/300/500 SCCM, theatmospheric pressure is for example 70 Pa, and the substrate temperatureis for example 360° C.

Next, a resist film is formed on this tungsten silicide film 36.Openings are formed in this resist film with a predetermined patterncorresponding to the cathode holes by the photolithography process. Theinside diameters of these openings correspond to the inside diameters ofthe cathode holes and for example are about 0.8 μm. The resist film isnot particularly limited, but for example a novolac-based g-line useresist can be used.

Next, the semiconductor substrate 30 on which this resist film is formedis placed in for example a general plasma etching device, where theetching is carried out by using the resist film 38 as a mask. The plasmaetching device is not particularly limited, but for example a microwaveelectron cyclotron resonance (ECR) plasma etching device, an inductivelycoupled plasma (ICP) etching device, a helicon plasma etching device, atranscoupled plasma (TCP) etching device, etc. can be exemplified.

First, by using for example an ECR etching device, the tungsten silicidefilm 36 and the polycrystalline silicon film 34 are continuously etchedunder the following conditions.

As the etching gas, a gas mixture of Cl₂ and O₂ is used. The flow ratioof Cl₂ /O₂ is determined to be for example 75/5 SCCM. The atmosphericpressure is for example 1.0 Pa. Further, the microwave power is forexample 900 W, the high frequency (RF) power is for example 50 W (2MHz), and the substrate temperature is for example 20° C.

Subsequently, the insulation layer 31 is subjected to the etching. Atthe etching, for example, an ECR type plasma etching device is used. Theetching conditions thereof are shown below.

As the etching gas, a gas mixture of CHF₃ and CH₂ F₂ is used. The flowratio of CHF₃ /CH₂ F₂ is determined to be for example 45/5 SCCM. Theatmospheric pressure is for example 0.27 Pa. Further, the microwavepower is for example 1200 W, the high frequency (RF) power is forexample 225 W (800 kHz), and the substrate temperature is for example20° C.

Conventionally, by the continuous etching of such a multiple layer film,the resist film 38 retreats due to an excessive overetching of the highenergy conditions. The side walls of the openings 40 are also shaved andthe tungsten silicide film 36 located in the lower layer thereof ispartially etched, thereby forming a tapered shape. The reason for thisis considered to be that the gate electrodes 35 and the insulation layer31 are subjected to the etching by the same resist film, therefore thetime during which the resist film is exposed to the plasma etchingbecomes longer than that by the conventional etching technique forforming the contact holes. In the present embodiment, however, thehydrogen-containing layer 33 is provided in the insulation layer 31,therefore the hydrogen produced when the hydrogen rich (several tens ofpercent by weight) hydrogen-containing layer 33 is etched increases theC/F ratio near the holes 44 and forms a depositing atmosphere, whereby afluorocarbon-based deposit as seen at the usual SiO₂ etching becomes theside wall protecting film and prevents the retreat of the photoresist.Accordingly, the overetching is not carried out up to the side walls ofthe openings of the gate electrodes 35. As a result, also a shoulderdrop of the tungsten silicide film 36 etc. can be prevented, and cathodeholes 44 having a good anisotropic shape can be formed.

Next, the resist film is removed by resist ashing. The resist ashing iscarried out by using O₂ of for example 500 SCCM and under conditions ofan atmospheric pressure of for example 3.0 Pa, a substrate temperatureof for example 200° C., and a high frequency (RF) power of for example300 W. In the step simultaneous with or after the time of removal ofthis resist film, also the side wall protecting film is removed.

Next, a peeling layer is formed on the tungsten silicide film 36 byusing the electron beam vapor deposition process or the like. Thepeeling layer is comprised by for example an aluminum metal layer. Thethickness of the peeling layer is not particularly limited, but is forexample about 50 nm. The substrate angle at the time of the electronbeam vapor deposition is preferably about 20 degrees (oblique incidentvapor deposition). The atmospheric pressure is for example 1.0 Pa.

Next, by using for example the electron beam vapor deposition process,the cathode-forming layer is deposited on the peeling layer. As thecathode-forming layer, preferably molybdenum (Mo) is used, but it isalso possible to use other high melting point metals or other metals andcompounds. The angle of the substrate at the time of the electron beamvapor deposition is preferably for example about 90 degrees. By formingthe cathode-forming layer to a thickness of for example about 1.0 μm onthe surface of the substrate 30 located in the bottom portion of thecathode holes 44, acute angle conical cathodes 50 are formed with auniform shape and height. The shapes of the cathodes 50, particularlythe heights, depend upon the time until the openings of the cathodeforming layer are closed. In the present embodiment, there is no taperand shoulder drop in the side walls of the openings of the tungstensilicide film 36, and therefore also the step coverage of thecathode-forming layer 48 becomes constant, the time until the openings48a are closed is constant, and thus the shapes of the cathodes 50,particularly the heights, can be made uniform.

Next, wet etching (for example about 30 seconds) is carried out byfluoric acid having a ratio of water:fluoric acid of 5:1, the peelinglayer comprised by aluminum or the like is removed by etching, and thecathode-forming layer located on this is lifted off. In the cathodeholes 44, the microcathodes 50 having a uniform shape and height remain.

Thereafter, a transparent panel on which the fluophor surface is formedis adhered onto the substrate 30 in the vacuum state to form the flatscreen display device of the present embodiment.

In the present embodiment, similar to the above embodiment, the colorfilter is comprised by fine particles of an inorganic metal oxide,therefore the transmittance of the obtained color filter is improved. Inaddition, in the color filter of the present embodiment, as shown inFIGS. 3A to 3C, the separability of the colors of red, green, and bluewith respect to the light emitted from the common single color fluophor15 is higher than that of the conventional filter, and as a result purerthree primary colors can be obtained from the single color light. Thiscontributes to the increase of the contrast and increase of the colorreproduction range.

Further, by forming the color filters and the fluophor layer by thescreen printing, a laminate structure in which the color filters 4R, 4G,and 4B and the fluophor layer 15 are well separated as layers isobtained, the luminance of the emission the fluophors is not lowered,the image quality is improved, and, at the same time, there is acontribution to the stability of the quality of the color flat screendisplay device.

Note that, the present invention is not limited to the above embodimentsand can be modified in various ways within the scope of the presentinvention.

For example, the present invention is not limited to a CRT or a flatscreen display device according to the above embodiments and can beapplied to also a color cathode ray tube such as a flat CRT or othercolor display devices such as a plasma display.

Next, the present invention will be explained in more detail based onexamples. Note that, in the following examples and comparative examples,parts and percents are based on weight unless otherwise specified.

EXAMPLE 1

A fluophor surface of a structure shown in the schematic sectional viewof FIG. 2 was formed on a transparent panel glass 32 by screen printing.In the present example, however, the single color fluophor layer 15 wasformed in place of the fluophor layers 15R, 15G, and 15B shown in FIG.2.

First, on the transparent panel glass 12, black stripes 2 were formedaccording to an ordinary method.

Next, so as to form the color filters 4R, 4G, and 4B on the blackstripes 2 by the screen printing, pastes of the respective colors wereprepared.

(A) R (red) paste

A mixture of 34 parts of red pigment (DEFICR 1007 made by Dowa KogyoCorp.) comprised of iron oxide (Fe₂ O₃) -based ultrafine particles, 15parts of a chemical absorbing type polymer dispersion agent (Solsperse(phonetic) made by ICI Corp.), and 51 parts of terpineol (Yasuhara YushiCorp.) was finely dispersed by an annular type media dispersion machine(Diamond Fine Mill made by Mitsubishi Heavy Industries Ltd.) to obtain amill base red having an intended particle size.

Subsequently, 46 parts of varnish obtained by dissolving 4 parts ofEtcell (phonetic) STD10 cps (ethyl cellulose made by Dow Chemical Corp.)in 42 parts of butyl diglycol acetate (made by Daicel Chemical Ltd.) byheating was added to 54 parts of the present mill base. These were mixedand dispersed by a triple-roll machine (made by Inoue Seisakusho Corp.).When the distribution of the particle size of the present paste wasmeasured by a centrifugal precipitation type particle size distributionmeasurement unit (SA-CP3 made by Shimadzu Seisakusho Corp.), the resultwas an average particle size of 0.03 pm. Further, looking at thedispersion rate of the other particles when the most frequent number ofparticles (particle size: 0.035 μm) was set as 100 percent, the numberof particles of 0.1 μm or more was 70 percent or more based on thenumber of all of the particles. The result of measurement of thisparticle size distribution is shown in FIG. 5A.

(B) B (blue) paste

A mixture of 37 parts of blue pigment (Dipyroxide TM Blue 3410(phonetic) of Dainichi Seika Corp.) made of ultrafine particles ofcobalt aluminate (CoO, Al₂ O₃), 10 parts of a chemical absorption typepolymer dispersion agent, and 53 parts of terpineol was finely dispersedby the same method as the production method of the R paste to obtain amill base blue having the intended particle size.

Subsequently, 32 parts of varnish obtained by dissolving 5.6 parts ofEtcell STD7 cps (ethyl cellulose made by Daicel Chemical Ltd.) in 26.4parts of butyl diglycol acetate by heating was added to 68 parts of thepresent mill base blue. These were mixed and dispersed by a triple-rollmachine.

When the distribution of the particle size of the present paste wasmeasured by the same method, the result was an average particle size of0.05 μm. Further, the distribution rate of other particles when the mostfrequent number of particles (particle size: 0.045 μm) was set as 100percent was equivalent to that of the R paste. The result of measurementof this particle size distribution is shown in FIG. 5B.

(C) G (green) paste

A mixture of 30 parts of green pigment (Dipyroxide TM Green 3320(phonetic) made by Dainichi Seika Corp.) composed by ultrafine particlesof TiO, ZnO, CoO, and NiO, 10 parts of a chemical absorbing type polymerdispersion agent, and 60 parts of terpineol was finely dispersed by thesame method as the production method of the R paste to obtain a millbase green having an intended particle size.

Subsequently, 24 parts of varnish obtained by dissolving 76 parts of thepresent mill base and 3.8 parts of Etcell 10 cps in 20.2 parts of butyldiglycol acetate by heating was added to this. These were mixed anddispersed by a triple-roll machine.

The distribution of particle size of the present paste was measured bythe same method. As a result, the average particle size diameter was0.06 μm. Further, the distribution rate of the other particles whensetting the most frequency number of particles (particle size: 0.045 μm)as 100 percent was the same level as that of the R paste. The result ofmeasurement of this particle size distribution is shown in FIG. 5C.

Mixing of printing suitability enhancement agent

In order to improve the screen suitability, use can be made of ultrafineparticles of aluminum oxide (Aluminum Oxide C made by Nihon AerosilCorp.) and calcium stearate (SC-100 made by Sakai Kagaku Corp.) as arheology enhancement agent.

The screen printing suitability changes depending upon the mesh (openingsize) of the screen, resist thickness, squeeze angle, printing pressure,printing speed, pattern precision, etc., and accordingly preferably alsothe rheology of the pigment pastes is appropriately controlled. Apreferred value of the measurement value by a rheometer made byRheometric Co. is shown below:

Steady-state viscosity: 200 to 800 Pa-S/25° C.

Complex elastic modulus: 5000 to 15000 dyne/cm²

By performing the screen printing by using the above pigment pastes, asshown in FIG. 2, color filters 4R, 4G, and 4B were formed. At the timeof the screen printing, a high precision low pressure screen printingmachine made by Microtec Corp. was used. Further, at the time of thescreen printing, the printing was performed on the surface of a panelglass 12 equipped with BM stripes (light shielding layer) 2 so that theB, R, and G adjoin different colors from each other.

Next, on these color filters, the single color fluophor layer 15 wasformed by the screen printing by using a fluophor slurry having a commoncolor (containing ZnO--Zn).

When four such fluophor surfaces were prepared and the transmittance wasmeasured for the filters, the results shown in FIGS. 6A to 6C wereobtained. FIG. 6A is a graph of the transmittances of red filters 4R-1to 4R-4 of four samples, FIG. 6B is a graph of transmittances of greenfilters 4G-1 to 4G-4 of four samples, and FIG. 6C is a graph oftransmittances of blue filters 4B-1 to 4B-4 of four samples. Thepercents of the transmittance, however, are the values where thetransmittance in a case where the color filter is not formed is set as100 percent.

As apparent from the results shown in FIGS. 6A to 6C, it was confirmedthat the color filters of the present example selectively allowed thelights of respective colors to pass therethrough in comparison with thecolor filter of the comparative example (conventional example) shown inFIG. 7.

Further, the panel glass formed in this way was installed in a CRT wherethe chromaticity point and the relative luminance were measured.

The chromaticity was measured by a Color Analyzer CA-100 made by MinoltaCorp. The measurement conditions were an acceleration voltage of 27 kVand a cathode current of 300 μA. The luminance B was measured by a ColorAnalyzer CA-100 made by Minolta Corp. The measurement conditions weresuch that a white color of 9300 K was manifested in a state where theCRT was installed in the set (GDM 19 inches).

The results of the measurement are shown in the following Table 1 andFIG. 8A.

                  TABLE 1                                                         ______________________________________                                        Fluophor ZnO:Zn                                                                          Chromaticity point                                                                       Relative                                                Filter film                                                                             x            y      luminance                                       ______________________________________                                        4R-1      0.459        0.500  21%                                             4R-2      0.512        0.470  15%                                             4R-3      0.567        0.419   7%                                             4R-4      0.595        0.389   4%                                             4G-1      0.230        0.460  66%                                             4G-2      0.220        0.503  52%                                             4G-3      0.226        0.541  39%                                             4G-4      0.225        0.585  24%                                             4B-1      0.179        0.349  56%                                             4B-2      0.171        0.340  50%                                             4B-3      0.134        0.284  33%                                             4B-4      0.116        0.280  16%                                             No filter 0.228        0.394  100%                                            ______________________________________                                    

Note: The relative luminance without a filter was set as 100 percent.

The relative luminance in the table is the value based on the value ofno filter as 100 percent.

Further, for comparison, the results of measurement of the chromaticityby using a color filter according to the conventional example (one usinga metal colloid and having a transmittance shown in FIG. 7) are shown inFIG. 8B.

As shown in Table 1 and FIG. 8A, it was confirmed that a CRT of a highluminance having a much wider color reproduction range than that of theconventional example could be realized in a CRT using the color filtersaccording to the present example.

Further, when the contrast of the CRT of the present example wasmeasured, it was confirmed that also the contrast was improved incomparison with that of the conventional example.

EXAMPLE 2

A CRT was produced in exactly the same way as that for above Example 1except that a fluophor layer composed of SnO₂ :Eu was formed in place ofthe fluophor layer composed of ZnO--Zn only on the red filters 4R-1 to4R-4.

When the chromaticity point and the relative luminance were measuredsimilar to Example 1, the results shown in Table 2 were obtained.

                  TABLE 2                                                         ______________________________________                                        Fluophor SnO.sub.2 :Eu                                                                   Chromaticity point                                                                       Relative                                                Filter film                                                                             x            y      luminance                                       ______________________________________                                        4R-1      0.598        0.401  60%                                             4R-2      0.600        0.399  56%                                             4R-3      0.607        0.393  37%                                             4R-4      0.614        0.385  23%                                             ______________________________________                                    

Note: The relative luminance without a filter was set as 100 percent.

As shown in Table 2, it was confirmed that, where a fluophor layeremitting red light is provided on the red filters 4R-1 to 4R-4, therelative luminance was further improved and the color reproduction rangewas increased over than that by the above Example 1.

EXAMPLE 3

In this example, a CRT was produced in the same way as the above Example1 except the fluophor surface of the panel glass shown in FIG. 2 wasformed by heat transfer printing and three primary color fluophor layerstripes were formed as the fluophor layers.

First, a transfer sheet was prepared. In order to prepare the transfersheet, a screen five-color machine made by Taiho Kikai Corp. was used.

A peeling layer made of acrylic resin was printed on the entire surfaceof a polyester film equipment filter having a thickness of 25 μm, alight shielding frame using graphite was printed, and then fluophorslurries of B, R, and G were printed. As the fluophor slurries, wellknown slurries were used. Subsequently, the color filter use pigmentpaste used in the Example 1 was superimposed on the common color of thefluophor printing surface and the screen printing was carried out.Further, an acrylic heat sealing agent was printed on the entire surfaceto thereby prepare the fluophor transfer sheet equipped with the colorfilter.

This was superimposed on the glass surface so that the heat sealingagent side of this transfer sheet was in close contact with the innersurface of the panel glass. The heat transfer was carried out under theconditions of 150° C. by using a rotary type heat transfer machine madeby Taihei Kogyo Corp. The color filter and the fluophor layer werethereby formed on the inner surface of the panel glass.

As explained above, according to the present invention, in the colordisplay device, an increase of the luminance, an increase of thecontrast, an increase of the color reproduction range, and animprovement of the ability to prevent reflection by outside light can beachieved.

What is claimed is:
 1. A color filter composition comprising:fineparticles of an inorganic metal oxide comprising 15 percent by weight orless of particles having a particle size of 0.1 μm or more based on theweight of all of the particles; and the fine particles furthercomprising at least 70 percent by weight green light transmissibleparticles of larger than 0.02 μm and smaller than 0.08 μm particle sizeor blue light transmissible particles of larger than 0.02 μm and smallerthan 0.08 μm particle size, wherein a visible light transmittance ofsaid color filter composition in a color filter after sintering is 50percent or more.
 2. A color filter composition as set forth in claim 1,further comprising a binder containing ethyl cellulose compounds and/orpolyvinyl alcohol (PVA) compounds.
 3. A color filter composition as setforth in claim 1, wherein the inorganic metal oxide contains at leastone of iron oxide, titanium oxide, nickel oxide, cobalt oxide, zincoxide, aluminum oxide and chromium oxide.
 4. A color filtercompositionhaving a spectral characteristic allowing visible light topass said color filter composition in the color filter, and comprisingfine particles of an inorganic metal oxide comprising 15 percent byweight or less of particles having a particle size of 0.1 μm or morebased on the weight of all of the particles and the fine particlesfurther comprising at least 70 percent by weight or more of particleshaving a particle size of larger than 0.02 μm and smaller than 0.08 μmbased on the weight of all of the particles, and a binder containingethyl cellulose compounds and/or a binder containing polyvinyl alcohol(PVA) compounds.
 5. A color filter composition as set forth in claim 4,wherein the fine particles comprise green light transmissible particlesof larger than 0.02 μm and smaller than 0.08 μm particle size or bluelight transmissible particles of larger than 0.02 μm and smaller than0.08 μm particle size.
 6. A color filter composition as set forth inclaim 4, wherein, a light transmittance of a specific light transmissionregion of the visible region of said color filter composition in a colorfilter after sintering is 50 percent or more.
 7. A color filtercomposition as set forth in claim 4, wherein the inorganic metal oxidecontains at least one of iron oxide, titanium oxide, nickel oxide,cobalt oxide, zinc oxide, aluminum oxide and chromium oxide.
 8. Apigment paste composition comprisingfine particles of an inorganic metaloxide containing 15 percent by weight or less of particles having aparticle size of 0.1 μm or more based on the weight of all of theparticles and containing 70 percent by weight or more of green lighttransmissible particles having a particle size of larger than 0.02 μmand smaller than 0.08 μm based on the weight of all of the particles,and a binder containing ethyl cellulose compounds and/or a bindercontaining polyvinyl alcohol (PVA) compounds wherein a lighttransmittance of a specific light transmission region of a visibleregion of said pigment paste composition is to be 50 percent or moreafter heat processing.
 9. A pigment paste composition as set forth inclaim 8, wherein the inorganic metal oxide contains at least one of ironoxide, titanium oxide, nickel oxide, cobalt oxide, zinc oxide, aluminumoxide and chromium oxide.
 10. A pigment paste composition comprisingfineparticles of an inorganic metal oxide containing 15 percent by weight orless of particles having a particle size of 0.1 μm or more based on theweight of all of the particles and containing 70 percent by weight ormore of blue light transmissible particles having a particle size oflarger than 0.02 μm and smaller than 0.08 μm based on the weight of allof the particles, and a binder containing ethyl cellulose compoundsand/or a binder containing polyvinyl alcohol (PVA) compounds wherein alight transmittance of a specific light transmission region of a visibleregion of said pigment paste composition is to be 50 percent or moreafter heat processing.
 11. A pigment paste composition as set forth inclaim 10, wherein the inorganic metal oxide contains at least one ofiron oxide, titanium oxide, nickel oxide, cobalt oxide, zinc oxide,aluminum oxide and chromium oxide.